The free radical-induced reaction of a saturated hydrocarbon with an unsaturated hydrocarbon is well known in the prior art. In addition, the prior art as exemplified by U.S. Pat. No. 2,562,369 has disclosed that a saturated hydrocarbon may be condensed with an olefin containing at least one chlorine atom on each of the doubly-bonded carbon atoms in the presence of a free radical generator to form an unsaturated chlorinated hydrocarbon. However, this prior art patent stated that it is essential that the chloroolefin contain at least two chlorine atoms per molecule since monochloroolefins do not give a condensation reaction of the type therein described. This belief, that the condensation required an olefinic compound possessing at least one halogen radical on each of the doubly-bonded carbon atoms, would lead one reasonably skilled in the art away from the discovery that the condensation between a saturated hydrocarbon and a chloromonoolefin in which the chlorine atom is attached to only one of the doubly-bonded carbon atoms may be effected in the presence of a free radical-generating compound and a promoter.
This invention relates to a process for the production of monochloro-substituted saturated compounds. More specifically, the invention relates to a process for the preparation of monochloro-substituted saturated compounds which comprises condensing a cycloalkyl hydrocarbon with a chloromonoolefin in which the chlorine atom is attached to one of the doubly-bonded carbon atoms, said condensation being effected in the presence of a free radical-generating catalyst and a promoter comprising a hydrogen chloride compound.
As was hereinbefore set forth, it has now been unexpectedly discovered that a saturated compound such as a cycloalkyl hydrocarbon may be condensed with a chloromonoolefin in which a chlorine atom is attached to only one of the doubly-bonded carbon atoms, the condensation being induced by a free radical-generating catalyst such as a peroxy compound and in the added presence of a promoter comprising a hydrogen chloride compound. The utilization of the promoter comprising the hydrogen chloride compound will produce a greater percentage conversion of the original reactants, namely, the saturated compound and the chloroolefin compound, and increase the yield of the monochloro-substituted saturated compound.
The products which are obtained by the condensation reaction of the present invention, namely, monochloro-substituted saturated compounds, are utilized in the chemical industry in various ways. For example, the heavier weight molecular monochloro-substituted saturated compounds may be converted to alcohols for further use in the preparation of detergents. Likewise, 2-chloroethylcyclohexane which may be prepared according to the process of this invention may be used as an intermediate for the preparation of phenylated ethylcyclohexane.
It is therefore an object of this invention to provide a process for the preparation of monochloro-substituted saturated compounds.
A further object of this invention is to provide an improved process for the obtention of a monochloro-substituted saturated compound by the use of a promoter thereby permitting more economic batch and continuous type processes to be employed.
In one aspect an embodiment of this invention resides in a process for the production of a monochloro-substituted saturated compound which is effected by condensing a saturated cycloalkyl hydrocarbon selected from the group consisting of a cycloalkane having from 5 to about 8 carbon atoms in the ring, a bicycloalkyl having from 10 to 16 carbon atoms in the rings and a polycycloalkane having from 6 to 14 carbon atoms in the rings with a chloromonoolefin possessing not more than 4 carbon atoms and having the chlorine atom attached to one of the doubly-bonded carbon atoms, in the presence of a free radical-generating peroxide catalyst at a temperature at least as high as the decomposition temperature of said catalyst and at a pressure of from 1 to about 100 atmospheres, and recovering the resultant monochloro-substituted saturated compound, and with the improvement which comprises effecting the reaction in the presence of a promoter comprising hydrogen chloride.
A specific embodiment of this invention is found in a process for preparing (2-chloroethyl)cyclohexane which comprises condensing cyclohexane with vinyl chloride at a temperature in the range of from about 130.degree. to about 140.degree. C. in the presence of a catalyst comprising di-t-butyl peroxide and a promoter comprising a hydrogen chloride compound and recovering the resultant (2-chloroethyl)cyclohexane an x-(1-chloroethyl)-y-(2-chloroethyl)cyclohexane.
Other objects and embodiments will be found in the following further detailed description of the present invention.
As hereinbefore set forth the present invention is concerned with a process for preparing monochloro-substituted saturated compounds in which a saturated compound comprising a cycloalkyl hydrocarbon is condensed with a monochloromonoolefin in which the chlorine atom is attached to one of the doubly-bonded carbon atoms in the presence of a free radical-generating catalyst and in the presence of a promoter comprising a hydrogen chloride compound. For purposes of this invention, the term "cycloalkyl hydrocarbon" as used in the present specification and appended claims will refer to monocycloalkanes, polycycloalkanes, and bicycloalkyls. As examples of these compounds, a cycloalkyl hydrocarbon may be exemplified by cyclohexane, ##STR1## a polycycloalkane may be exemplified by decahydronaphthalene ##STR2## and by bicyclo[2.2.1]heptane ##STR3## and a bicycloalkyl may be exemplified by bicyclohexyl ##STR4## Each of these may contain alkyl substituents having from 1 to about 10 or more carbon atoms.
The reaction is effected under conditions which include an elevated temperature of at least as high as the initial decomposition temperature of the free radical-generating catalyst. In addition, another reaction condition involves pressure, said pressure ranging from about atmospheric to about 100 atmospheres or more. When superatmospheric pressures are employed, said pressures are afforded by the introduction of vaporized reactants or a substantially inert gas such as nitrogen into the reaction zone. Another variable which is employed is the amount of reactants, the saturated compound comprising a cycloalkyl hydrocarbon usually being present in a mole ratio in the range of from about 1:1 to about 10:1 moles per mole of monochloromonoolefin in which the chlorine atom is attached to one of the doubly-bonded carbon atoms.
Examples of suitable saturated compounds comprising cycloalkyl hydrocarbons which are utilized as one of the starting materials in the process of this invention include monocycloalkanes containing from 5 to about 8 carbon atoms in the ring such as cyclopentane, cyclohexane, cycloheptane, cyclooctane; polycycloalkanes having from 6 to 14 carbon atoms in the ring such as bicyclo[2.2.1]heptane, decahydronaphthalene, tetradecahydroanthracene, bicycloalkyls having from 10 to 16 carbon atoms in the ring such as bicyclopentyl, bicyclohexyl, bicycloheptyl, bicyclooctyl.
Suitable chloromonoolefins which may be condensed with the aforementioned saturated compounds will contain up to 4 carbon atoms and will have the chlorine atom attached to one of the doubly-bonded carbon atoms. Specific examples of these chloromonoolefins will include vinyl chloride, 1-chloro-1-propene, 2-chloro-1-propene, 1-chloro-1-butene, 2-chloro-1-butene and 2-chloro-2-butene.
The catalytic compositions of matter which are used in the process of the present invention comprise organic peroxides which are designated as free radical-generating catalysts. Examples of these catalysts which may be used include, in particular, the disubstituted hydrogen peroxides such as di-t-butyl peroxide, t-butyl perbenzoate, benzoyl peroxide, etc. It is also contemplated within the scope of this invention that hydroperoxides such as acetyl hydroperoxide and t-butyl hydroperoxide may also be used although not necessarily with equivalent results.
The reaction temperatures should be at least as high as the initial decomposition temperature of the free radical-generating catalysts, such as the peroxide compound, in order to liberate and form free radicals which promote the reaction. In selecting the particular reaction temperature for use in the process of the present invention two considerations must be taken into account. First, sufficient energy by means of heat must be supplied to the reaction system so that reactants, namely, the cycloalkyl hydrocarbon and the chloroolefin in which the chlorine is attached to one of the doubly-bonded carbon atoms, will be activated sufficiently for condensation to take place when free radicals are generated by the catalyst. Second, free radical-generating catalysts such as the peroxy compounds, particularly organic peroxides, decompose at a measurable rate with time in a logarithmic function dependent upon temperature. The rate of decomposition can be, and ordinarily is, expressed as the half-life of the peroxide at a particular temperature. For example, the half-life in hours of di-t-butyl peroxide is 17.5 hours at 125.degree. C., 5.3 hours at 135.degree. C., and 1.7 hours at 145.degree. C. (calculated from data for the first 33% decomposition). A reaction system temperature can be selected so that the free radical-generating catalyst decomposes smoothly with the generation of free radicals at a half life which is not too long. In other words, sufficient free radicals must be present to induce the present chain reaction to take place, and these radicals must be formed at a temperature at which the reactants are in a suitably activated state for condensation. When the half life of the free radical-generating catalyst is greater than 10 hours, radicals are not generated at a sufficient rate to cause a reaction of the process of the present invention to go forward at a practical rate. Thus, the reaction temperature may be within the range of from about 50.degree. to about 300.degree. C. and at least as high as the decomposition temperature of the catalyst, by which is meant a temperature such that the half life of the free radical-generating catalyst is not greater than 10 hours. Since the half life for each free radical-generating catalyst is different at different temperatures, the exact temperature to be utilized in a particular reaction will vary. However, persons skilled in the art are well acquainted with the half life versus temperature data for different free radical-generating catalysts. Thus it is within the skill of one familiar with the art to select a particular temperature needed for any particular catalyst. However, the operating temperatures generally do not exceed the decomposition temperature of the catalyst by more than about 150.degree. C. since free radical-generating catalysts decompose rapidly under such conditions. For example, when a free radical-generating catalyst such as t-butyl perbenzoate is used having a decomposition temperature of approximately 115.degree. C. the process is run at a temperature ranging from 115.degree. to about 265.degree. C. When di-t-butyl peroxide having a decomposition temperature of about 130.degree. C. is used, the process is run at a temperature ranging from 130.degree. to about 280.degree. C. Higher reaction temperatures may be employed, but little advantage is gained if the temperature is more than the hereinbefore mentioned 150.degree. C. higher than the decomposition temperature of the catalyst. The general effect of increasing the operating temperature is to accelerate the rate of condensation reaction between the chloroolefin in which the chlorine atom is attached to one of the doubly-bonded carbon atoms and the saturated compound comprising a cycloalkyl hydrocarbon. However, the increased rate of reaction may be accompanied by a certain amount of undesired side reactions such as polymerization of the chloroolefin.
It is contemplated within the scope of the present invention that a promoter comprising a hydrogen chloride compound will enhance the quantity of monochloro-substituted saturated compound produced in the reaction. By "hydrogen chloride compound" is meant either anhydrous hydrogen chloride or aqueous hydrochloric acid. The effect upon the mechanism of the hereinbefore set forth reaction is that of increasing the yield of the monochloro-substituted product. The mechanism of the action of the hydrogen chloride (which exhibits a marked and unique effect on free radical-induced reactions) is shown by the following example: ##STR5##
The so-formed cyclohexyl radical starts a new cycle and the (2-chloroethyl)cyclohexane is produced by the resulting chain reaction. In the absence of hydrogen chloride, the following chain reaction occurs: ##STR6## The chloroethylcyclohexane radical abstracts a hydrogen atom more rapidly from hydrogen chloride than from cyclohexane and therefore 2-chloroethylcyclohexane is formed more rapidly (and hence in higher yield) than in the absence of hydrogen chloride. The desired compound is then formed before the chloroolefin or the 2-chloroethylcyclohexyl radical undergo polymerization or other side reactions.
The process of this invention may be effected in any suitable manner and may comprise either a batch or continuous operation. For example, when a batch type operation is employed, the reactants comprising the cycloalkyl hydrocarbon and the monochloromonoolefin containing up to 4 carbon atoms in which the chlorine atom is attached to one of the doubly-bonded carbon atoms are placed in an appropriate apparatus along with a free radical-generating catalyst and a promoter comprising a hyrogen chloride compound. In the event that atmospheric pressure is to be employed, the reaction vessel is then heated to a predetermined operating temperature which is at least as high as the decomposition temperature of the free radical-generating catalyst. After maintaining the reactants in the reaction vessel at this temperature for a period of time which may range from about 0.5 up to about 30 hours or more in duration, the heating is discontinued and the vessel is allowed to return to room temperature. The reaction mixture is then recovered, separated from the catalyst and the promoter and subjected to conventional means of purification and separation, said means including washing, drying, extraction, evaporation, fractional distillation, etc., whereby the desired monochloro-substituted saturated compound is recovered. Alternatively, if superatmospheric pressures are to be employed in the reaction, the reactants are charged to a pressure vessel such as a rotating autoclave which contains the free radical-generating catalyst and the hydrogen chloride compound which acts as a promoter. The autoclave is sealed and a substantially inert gas such as nitrogen or helium may be pressed in; the inert gas is added in order to have sufficient pressure at the reactor temperature to maintain a substantial portion of the reactants in the liquid phase. The autoclave is then heated to the desired operating temperature and maintained thereat for a predetermined residence time. At the end of this time, heating is discontinued, the autoclave is allowed to return to room temperature and the excess pressure is discharged. The autoclave is opened and the reaction mixture is then treated in a manner similar to that hereinbefore set forth whereby the desired monochloro-substituted saturated compound is separated and recovered.
It is also contemplated within the scope of this invention that the reaction process for obtaining a monochloro-substituted saturated compound may be effected in a continuous manner of operation. When such a type of process is employed, the reactants comprising a cycloalkyl hydrocarbon and the monochloromonoolefin containing up to 4 carbon atoms in which the chlorine atom is attached to one of the doubly-bonded carbon atoms are continuously charged to a reaction vessel under conditions of continuous agitation as are the free radical-generating catalyst and the promoter comprising a hydrogen chloride compound. If so desired, one or more of the above may be admixed prior to entry into said reaction vessel and the mixture charged thereto in a single stream. After completion of the desired residence time, the reactor effluent is continuously withdrawn and subjected to conventional means of separation whereby the desired monochloro-substituted saturated compound or compounds are recovered, while any unreacted starting material comprising the cycloalkyl hydrocarbon or the monochloromonoolefin are recycled to the reaction zone to form a portion of the feed stock.
Examples of monochloro-substituted saturated compounds which may be prepared according to the process of this invention will include (2-chloroethyl)cyclohexane, x-(1-chloroethyl)-y-(2-chloroethyl)cyclohexane, 1-chloro-2-cyclohexylpropa ne, 1-chloro-2-cyclohexylbutane, (2-chloroethyl)cycloheptane, (2-chloroethyl)cyclooctane, (2-chloroethyl)decahydronaphthalene, 1-chloro-2-decahydronaphthylpropane, 1-chloro-2-decahydronaphthylbutane, (2-chloroethyl)bicyclohexyl, (2-chloroethyl)bicycloheptyl, 1-chloro-2-cyclopentylbutane, etc. It is to be understood that the aforementioned monochloro-substituted saturated compounds are only representative of the classes of compounds which may be prepared and that the present invention is not necessarily limited thereto.